Emulsions used on the skin may contain one or more salt based cosmetic astringents. For example, a common salt based cosmetic astringent for an emulsion used on the skin is an aluminum based salt. Common examples of aluminum based salts include Ammonium and Potassium Alum, Aluminum Triphosphate, Sodium aluminum Phosphate, Aldioxa, Aluminum Stearate, Aluminum Distearate Aluminum Sulfate, Aluminum Dimyristate, Aluminum Calcium Sodium Silicate, and Aluminum Citrate. However, if the concentration of salt based cosmetic astringent is high enough in some circumstances, the emulsion will not be stable.
For instance, such emulsions tend to de-emulsify in storage, especially at temperatures encountered in warmer climates. They also de-emulsify when subjected to temperatures that cycle between hot and cold. It is believed that the instability in such emulsions including a salt based cosmetic astringent is due to the high ionic strength of the salts.
What is needed is an emulsion system that is stable in the presence of high concentrations of salt based cosmetic astringents.